Will serve as white collar defense lawyer for Nixon Peabody

Middlesex County District Attorney Gerry Leone will join Nixon Peabody LLP as partner in the lawfirm’s government investigations and white collar defense practice in Boston, the firm announced Tuesday.

Leone says he plans to step down on April 12 and begin work with the firm on April 29.

Leone previously said he would not run for a third term, but had not indicated plans to leave office early.

“After dedicating myself to protecting and serving others and impacting lives in public service for the last twenty years, I’m excited about the opportunity to take on new challenges and provide service to others in a different capacity,” Leone said in a news release.

Last week, the same lawfirm announced former Massachusetts U.S. Senator Scott Brown joined the law firm as counsel in the firm’s Boston office, focusing on business and governmental affairs.

Leone, a Democrat, announced several weeks ago he would not seek another term, leading to speculation he was preparing for a possible run for the open U.S. Senate seat, or perhaps contemplating running for Massachusetts governor.

He issued a statement last month saying that while the U.S. Senate is a wonderful public service opportunity, it was not the right next step for him.

Gov. Deval Patrick would name a new district attorney to fill out the remainder of Leone's term, which runs through the end of 2014.